1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording apparatus for recording an image by discharging ink onto a recording medium.
2. Related Background Art
In the field of ink jet recording head and ink jet recording apparatus, there is conventionally known to use pigment-containing black ink for forming a black image excellent in print density, print quality, moisture resistance and light resistance particularly on plain paper or to use an ink set capable of preventing a bleeding phenomenon generated at the boundary of an image area printed with black ink and an image area printed with color ink or an uneven white image aberration (hereinafter called xe2x80x9cwhite fogxe2x80x9d) generated in a black image area at the boundary with color ink.
As representative technologies, the Japanese Patent Applications Laid-open Nos. 6-106841, 9-1188505, 11-334101 and 11-343441 and the U.S. Pat. Nos. 5,428,383, 5,488,402 and 5,976,230 disclose an ink set capable of reducing the bleeding phenomenon and composed of black ink and color inks of which at least one is mutually reactive with the black ink while the remainder is not reactive with the black ink, and an ink jet recording method utilizing such ink set. In order to prevent the bleeding at the boundary between a print area with the black ink and a print area with a color ink not reactive with the black ink, there is particularly disclosed a printing method in which the color ink having the reactivity is printed in superposed manner in the black ink print area (such method being hereinafter called xe2x80x9cunderprintingxe2x80x9d).
As the black ink and the color ink mutually reactive therewith, to be employed in such underprinting method, there is known a combination of a black ink containing a black coloring material including a hydrophilic radical and a mutually reactive color ink containing a reactive agent consisting of a metal ion. When these inks are coated on the recording medium and are mixed thereon to induce a reaction between the hydrophilic radical and the metallic ion, there is generated a precipitate of the black coloring material. Thus the black coloring material can be prevented from moving to the print area of the non-reactive ink adjacent to the print area of the black ink, thereby reducing the bleeding phenomenon generated between the print area of the black ink and the print area of the non-reactive color ink.
However the investigation of the present inventors has newly revealed the following drawbacks on the ink jet recording head and the ink jet recording apparatus employed in such underprinting method.
A first drawback is that a higher concentration of metal ions in the color ink for increasing the mutual reactivity with the black ink is desirable for reducing the bleeding phenomenon or the white fog phenomenon but results in deterioration of the ink discharging face of the recording head by the metal ions contained in the ink mist deposited on the ink discharging head or an increased viscosity of the ink resulting from a higher concentration of the metal ions added in the ink thereby deteriorating the discharge stability of the ink. In order to avoid such drawback, it is necessary to reduce the entire amount of the metal ions added to the color ink as far as possible while reducing the bleeding and white fog phenomena.
A second drawback is that the aggregate of the metal ions contained in the reactive ink is deposited on the end surface of a wiper, which is provided in the ink jet recording apparatus for wiping the ink discharge face of the recording head, thereby hindering the recovery of the performance of the recording head by the wiper. It is already known to provide wiper cleaning means for cleaning the wiper thereby restoring the wiping performance of the wiper, but it is still difficult to remove the aggregate, if once formed, by such wiper cleaning means and the wiper cleaning means becomes costly if such removing function is added.
A third drawback is that the reduction of the bleeding and white fog phenomenon may result in a reduced print speed, depending on the layout of the arrays of the discharging ports in the ink discharging recording head.
In consideration of the foregoing, an object of the present invention is to provide an ink jet recording head capable of minimizing the entire amount of the metal ions added to the color ink while reducing the bleeding and white fog phenomena. It is also an object of the present invention to provide an ink jet recording head capable of reducing the bleeding and white fog phenomena while preventing the loss in the recording speed.
Another object of the present invention is to provide an ink jet recording apparatus capable of avoiding deposition of the coagulate of the metal ions contained in the reactive ink on the end surface of the wiper. It is also an object of the present invention to provide an ink jet recording apparatus capable of reducing the bleeding and white fog phenomena while preventing the loss in the recording speed.
The above-mentioned objects can be attained, according to the present invention, by an ink jet recording head provided with plural arrays of discharge ports for discharging plural inks of at least three kinds in which a first ink and at least one of other inks are mutually reactive, wherein, in an array of the discharge ports having a relatively shorter distance from the print obtained by an array of the discharge port for the aforementioned first ink, there is introduced an ink showing a mutual reactivity equal to or higher than that of the ink introduced into an array of the discharge ports having a relatively longer distance from the print obtained by the aforementioned array of the discharge ports.
In the ink jet recording head of the present invention having the above-described configuration, the mutual reactivity, with the first ink, of the inks introduced into the arrays of the discharge ports other than the array for the first ink is highest in the ink introduced into the array having the shortest print distance from the print obtained from the array of the discharge ports for the first ink and becomes lower with the increase in the print distance. Such mutual reactivities of the inks introduced into the arrays of the discharge ports other than the array for the first ink, being lowered in succession with the increase of the print distance from the print by the first ink allows to reduce the entire concentration of the reactive agents (metal ions) in the reactive ink while reducing the bleeding and white fog phenomena, thereby simultaneously achieving higher quality of the printed image and higher reliability of the recording head.
According to the present invention, there is also provided another ink jet recording head provided with plural arrays of discharge ports for discharging plural inks of at least three kinds in which a first ink and at least one of other inks are mutually reactive, wherein, in an array of the discharge ports having a relatively shorter distance from an array of the discharge port for the aforementioned first ink, there is introduced an ink showing a mutual reactivity equal to or relatively higher than that of the ink introduced into an array of the discharge ports having a relatively longer distance from the aforementioned array of the discharge ports.
In such another ink jet recording head of the present invention, the mutual reactivity, with the first ink, of the inks introduced into the arrays of the discharge ports other than the array for the first ink is highest in the ink introduced into the array having the shortest distance from the array of the discharge ports for the first ink and becomes lower with the increase in the distance. Such mutual reactivities of the inks introduced into the arrays of the discharge ports other than the array for the first ink, being lowered in succession with the increase of the distance from the array for the first ink allows to reduce the entire concentration of the reactive agents (metal ions) in the reactive ink while reducing the bleeding and white fog phenomena, thereby simultaneously achieving higher quality of the printed image and higher reliability of the recording head.
Also there may be adopted a configuration in which the aforementioned first ink is black ink and the inks other than the first ink are color inks.
Also there may be adopted a configuration in which the aforementioned color ink showing the mutual reactivity with the aforementioned black ink is introduced only in an array of the discharge ports having the shortest print distance from the black print by the array of the discharge ports for the first ink.
In addition, there may be adopted a configuration in which the aforementioned color ink showing the mutual reactivity contains metal ions.
Furthermore, there may be adopted a configuration in which the aforementioned metal ion is at least a polyvalent metal cation selected from Mg2+, Ca2+, Cu2+, Co2+, Ni2+, Feg2+, La3+, Nd3+, Y3+ and Al3+.
Furthermore, there may be adopted a configuration in which the aforementioned color ink showing the mutual reactivity contains a metal salt in an amount of 0.1 to 15 wt. % with respect to the total weight of the color ink.
Furthermore, there may be adopted a configuration in which the black ink contains a salt and employs a black pigment as the coloring material.
According to the present invention, there is also provided an ink jet recording apparatus mounted with an ink jet recording head provided with plural arrays of discharge ports for discharging plural inks of at least three kinds in which a first ink and at least one of other inks are mutually reactive and adapted to execute recording by discharging ink from the ink jet recording head and depositing such ink onto a recording medium, wherein the ink jet recording head is so constructed that, in an array of the discharge ports having a relatively shorter distance from an array of the discharge port for the aforementioned first ink, there is introduced an ink showing a mutual reactivity equal to or relatively higher than that of the ink introduced into an array of the discharge ports having a relatively longer distance from the aforementioned array of the discharge ports.
Also there may be adopted a configuration in which the aforementioned first ink is black ink and the inks other than the first ink are color inks.
Also the ink jet recording apparatus of the present invention is mounted with the ink jet recording head of the present invention and is adapted to execute recording by discharging ink from the ink jet recording head and depositing the ink onto the recording medium.
According to the present invention, there is also provided an ink jet recording apparatus mounted with an ink jet recording head of the present invention and adapted to execute recording by discharging ink from the ink jet recording head and depositing the ink onto the recording medium and further provided with wiring means for moving a wiper in contact with the ink discharging face of the ink jet recording head thereby cleaning the ink discharging face, wherein the wiper, in wiping the portion of the plural arrays of the discharge ports other than the array for the aforementioned first ink on the ink discharging face, executes wiping operation on the arrays of the discharge ports in succession in the increasing order of the print distance from the print by the array of the discharge ports for the first ink.
In the above-described ink jet recording apparatus of the present invention, the wiping operation is executed in succession from an array of the discharge ports in which an ink having a relatively high concentration of the reactive agent (metal ions) is introduced to an array of the discharge ports in which an ink having a relatively low concentration of the reactive agent is introduced, whereby the ink of a relatively high concentration of the reactive agent, impregnated at first in the wiper, is diluted with the ink or a relatively low concentration of the reactive agent, impregnated later in the wiper, so that the concentration of the reactive agent becomes lower at least at the end portion of the wiper (in contact with the discharge port-bearing face of the recording head) thereby easily preventing the deposition of the aggregate of the reactive agent on the end surface of the wiper.